Digestive Dissection

We will explore the digestive system of a fetal pig and compare it to that of humans. The dissection will provide valuable insights into the anatomical structures and functions of the pig's digestive system, allowing us to draw parallels to our own digestive processes. By examining the external features, dissecting the head and neck region, and exploring the general internal anatomy, we will gain a comprehensive understanding of the similarities and differences between the fetal pig and human digestive systems.

Objectives

·         To identify and compare the external features of the fetal pig's digestive system to humans.

·         To examine the structures involved in ingestion, mastication, and taste perception.

·         To investigate the structures and functions of the organs involved in digestion, absorption, and elimination.

·         To gain a deeper understanding of the adaptations and evolutionary aspects of the digestive system in mammals.

Materials

·         Fetal pig

·         Dissecting kit

·         PPE: Gloves, Goggles

Fetal Pig Digestive System Dissection

1.       Determine the sex of the fetal pig:

a.       Female: Locate the urogenital opening ventral to the anus and the small genital papilla.

b.       Male: Identify the scrotal sac ventral to the anus and the urogenital opening posterior to the umbilical cord.

2.       Expose the structures of the mouth and pharynx:

a.       Insert a pair of scissors into the angle of the lips and cut posteriorly through the cheek.

b.       Open the mouth while cutting, following the curvature of the tongue.

c.        Hold down the tongue and continue the incision dorsal to it, extending into the opening of the esophagus.

d.       Repeat the procedure on the other side to expose the mouth and pharynx structures.

3.       Examine the oral cavity:

a.       Note the erupted deciduous canine and/or incisor teeth.

b.       Observe the developing teeth by making an incision in a bulge of the gums.

c.        Locate the papillae on the tongue's surface, especially near the base and along the anterior margins.

d.       Identify the anterior portion formed by the hard palate supported by bone and cartilage.

e.       Observe the posterior portion formed by the soft palate.

f.         Observe the oropharynx, which is the posterior extension of the nasopharynx.

g.       Note that the oropharynx may be difficult to visualize due to the incisions.

4.       Make incisions in the abdominal region:

a.       Use a sharp scalpel to make a small incision about ½-inch above the umbilical cord.

b.       Cut along the midsagittal line on the ventral surface, extending upward toward the neck.

c.        Continue the incision down to the pelvic region:

d.       Cut down to the caudal end of the pelvic region, leaving a ½-inch border around the umbilical cord.

e.       Stop the cut about one inch short of the anus.

f.         Make two lateral incisions just in front of the hind legs.

g.       Lift the lateral flaps of ribs, skin, and muscle on each side.

h.       Cut the diaphragm, which is attached to the inside body wall, allowing the ventral body wall flaps to be peeled open.

i.         Rinse the cavities of the pig in a sink if necessary, being careful to keep the organs in place.

5.       Identify the digestive organs in the abdomen:

a.       Locate the liver, a large, multilobed structure under the lungs and diaphragm.

b.       Lift up the lobes of the liver on the right side to find the small, green, saclike organ called the gallbladder.

c.        Observe the esophagus, which lies directly behind the trachea and extends from the neck to the entry into the stomach.

d.       Identify the stomach, a saclike organ situated under the liver on the left side.

                                                               i.      Cut open and clean the inside of the stomach, then compare the cardioesophageal and pyloric sphincters.

e.       Locate the duodenum, the first part of the small intestine attached to the right side of the stomach.

f.         Observe the pancreas, a clump of pinhead-sized grapes that begins in the loop between the stomach and duodenum and ends near the spleen on the left side.

g.       Identify the jejunum and ileum, the coiled remainder of the small intestine.

                                                               i.      Cut the mesentery away from the small intestine until it’s completely straight.

h.       Locate the appendix, a pinkie-like blind pouch at the junction of the ileum and cecum.

i.         Observe the colon, the darker, thicker, coiled portion of the large intestine.

j.         Identify the rectum, the last one to two inches of the large intestine leading to the anus.

Draw below, the alimentary canal (mouth to anus) of your fetal pig with all of its attached accessory organs. Then draw the same for a human.  Label and compare the two species.

Review Questions

1.       What are the organs involved in the human digestive system?
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2.       How does the process of digestion occur in the small intestine?
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3.       How does the digestive system respond to the consumption of high-fat foods?
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4.       How do the muscular walls of the stomach aid in the process of digestion?
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5.       What are some strategies that can be employed to improve digestion?
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6.       How does aging affect the digestive system?
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7.       What is the role of the liver in the digestive system? ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

8.       How does the process of peristalsis aid in the movement of food through the digestive system?
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9.       How can certain medications affect the digestive system?
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10.    How does the digestive system interact with other systems in the body? ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________